In recent years, a self-luminous display device using a light-emitting element (EL element) employing an electroluminescence (hereinafter referred to as “EL”) phenomenon has been developed as a display device instead of a liquid crystal display device.
The light-emitting element employing the EL phenomenon can emit light at a voltage from several volts to several tens volts. The light-emitting element is a self-emitting element. Therefore, the light-emitting element has wide viewing angle and high viewability. Further, the light-emitting element is a complete solid element having a thin-film shape. Therefore, attention is attracted from the viewpoint of saving space and portability.
Since the light-emitting element is a surface light source, the light-emitting element is considered to be applied to a backlight of a liquid crystal display device or a light source of an illumination.
In recent years, the research and development of the light-emitting element employing the EL phenomenon have been actively made. The light-emitting element has a configuration in which a functional layer containing at least a light-emitting layer is provided between positive and negative electrodes. The light-emitting element emits light by using release of light during deactivation of excitons that are generated by injecting electrons (e−) and holes (h+) into the light-emitting layer and causing recombination.
To realize a high-resolution EL display device as a display device using such a light-emitting element, use of a white light-emitting element is effective. In the white light-emitting element, vapor deposition by selectively patterning vapor deposition using a fine vapor deposition mask is not needed.